Osisko Development Appoints Vice President, Sustainable Development

MONTREAL, May 19, 2026  — Osisko Development Corp. (NYSE: ODV, TSXV: ODV) (“Osisko Development” or the “Company”) is pleased to announce the appointment of Mr. Greg Perrins as Vice President, Sustainable Development, effective May 18, 2026.

“We are pleased to welcome Greg to the Osisko Development team, where his deep knowledge of and experience in Indigenous relations and public sector engagement in BC will further strengthen our approach to sustainable project development,” stated Sean Roosen, Chairman and CEO.

Mr. Perrins is an Indigenous relations professional with over 15 years of experience in leadership roles across the natural resource sector in British Columbia. Most recently, he served as Senior Manager, Indigenous Relations at BC Hydro, a fully integrated public utility, where he supported engagement and relationship-building initiatives with Indigenous Nations across the province. Prior to his role at BC Hydro, Mr. Perrins spent the majority of his career working for the Province of British Columbia, including roles with the Ministry of Energy, Mines and Low Carbon Innovation, the Ministry of Indigenous Relations and Reconciliation, and the BC Oil and Gas Commission. Mr. Perrins holds a Master of Public Administration degree from the University of Victoria, a Bachelor of Social Work degree from Dalhousie University, and a Bachelor of Arts degree from the University of Regina.

ABOUT OSISKO DEVELOPMENT CORP.

Osisko Development Corp. is a continental North American gold development company focused on past producing mining camps with district-scale potential. The Company’s objective is to become an intermediate gold producer through the development of its flagship, fully permitted, 100%-owned Cariboo Gold Project, located in central British Columbia, Canada. Its project pipeline is complemented by the Tintic Project located in the historic East Tintic mining district in Utah, U.S.A., a brownfield property with significant exploration potential, extensive historical mining data, and access to established infrastructure. Osisko Development is focused on developing long-life mining assets in mining-friendly jurisdictions while maintaining a disciplined approach to capital allocation, development risk management, and mineral inventory growth.

For further information, contact:

Sean Roosen	Philip Rabenok
Chairman and CEO	Vice President, Investor Relations
Email: sroosen@osiskodev.com	Email: prabenok@osiskodev.com
Tel: +1 (514) 940-0685	Tel: +1 (437) 423-3644

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